diff --git a/site_ansto/Makefile b/site_ansto/Makefile
index 145ff726..765dcaaf 100644
--- a/site_ansto/Makefile
+++ b/site_ansto/Makefile
@@ -16,7 +16,8 @@ default: all
 EXTRA=nintf.o
 PSI_CLEAN_MATRIX = rm -f ../*.o; $(MAKE) -C ../matrix $(MFLAGS) clean
 PSI_CFLAGS = -I./ -I$(HDFROOT)/include -DHDF5 -DNXXML\
-       -DCYGNUS -DNONINTF -g $(DFORTIFY) -Wall
+       -DCYGNUS -DNONINTF -g $(DFORTIFY)\
+	   -Wall -Wextra -Wno-unused
 PSI_SLIBS = matrix/libmatrix.a
 PSI_LIBS =  -L$(HDFROOT)/lib $(NILIB)\
        -ltcl8.4 $(HDFROOT)/lib/libhdf5.a  \
@@ -35,7 +36,12 @@ PSI_LIBS =  -L$(HDFROOT)/lib $(NILIB)\
 # ANSTO rules and variables
 CC       = gcc
 INCFLAGS = -Ihardsup  -I.. -I/opt/gnome/include
-CFLAGS = -g $(INCFLAGS)  -Wno-unused -Wno-comment -Wno-switch -Wall
+# NOTE -std=gnu99 adds c99 support with gnu extensions, it eliminates implicit function warnings 
+# for c99 functions like roundf.  We don't use -std=c99 because it generates compiler errors in
+# code modules that use the timeval struct without including sys/time.h, c99 also generates
+# implicit function declaration warnings on string functions like strdup.
+DEBUGFLAGS = -Wall -Wextra -Wno-unused -Wno-comment -Wno-switch
+CFLAGS = -g $(INCFLAGS) $(DEBUGFLAGS) -std=gnu99
 HDFROOT=/usr/local
 
 SRC = ./../..